1. Field of the Invention
This invention relates to an optical recording-reproducing method for an optical recording medium containing a monomolecular film of a diacetylene derivative compound or its built-up film, particularly to an optical recording-reproducing method employing an IR-ray laser of 800-900 nm as the optical writing means and a visible light of 500-750 nm as the optical recording-reading means and to a device by using the same.
2. Description of the Related Art
Recently, optical discs are to the fore of interest among office automations. Since optical discs are capable of recording and storing a large amount of documents and literature in one sheet, documents in an office can be pigeonholed or managed with good efficiency. Various recording media have been investigated for such an optical disc, and those utilizing organic materials are attracting attention because of low price and easiness in manufacture.
As such an organic material for recording medium, a diacetylene derivative compound has been known and a recording technique employing said compound for a laser recording medium by utilizing the thermal color change property of said compound is disclosed in Japanese Patent Laid-Open No. 14780/1981. However, in this specification, there is no description about what kind of laser has been employed or has to be used, but there is only a description that recording was performed by use of a laser.
The present inventors have investigated about laser recording of the diacetylene derivative compound by use of various kinds of laser and consequently confirmed that, while thermal color change recording may be feasible by use of a laser scale and high output laser such as argon laser, etc., no laser recording is practicable when a semiconductor laser of small model and relatively low output (wavelength: 800 to 850 nm) was used. However, a practical recording medium of an optical disc, etc. is desired to have a capability of optical writing with a semiconductor laser of small model and low output, and of reading with an emission diode or a laser of small model.
Further, the recording layer of this recording medium comprises the diacetylene derivative compound as described above, fine crystalline powder of which is dispersed in a binder, and hence the molecules of the diacetylene derivative compound are randomly oriented within the recording layer, whereby such inconveniences may be caused that light absorptivity or reflectivity may differ and the degree of the chemical reactions may vary depending on the position on the medium. Thus, it cannot necessarily be suitable for high density recording.